Apparatus for condensing zinc vapor



Dec. 28, 1948. c, w K ETAL APPARATUS FOR counmnsme zmc VAPOR 2 Sheets-Sheet 1 Filed July 1. 1947 INVENTORS 7.7mm, B

ATTORNEYS D'ec- 28, 1948- E. c. HANDWERK ET AL APPARATUS FOR CONDENSING ZINC VAPOR 2 Sheets Shset 2 Filed July 1, 19.47

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ATTO R N EYS Patented Dec. 28, 1948 I APPARATUS FOR CONDEN SIN G ZINC VAPOR Erwin C. Handwerk and George T. Mahler, Palmerton, Pa., assign'ors to The New Jersey Zinc Company, New York, N. Y., a corporation 01'.

New Jersey Application July 1, 1947, Serial No. 758,288

3 Claims.

This invention relates to condensing zinc vapor, and has for its object an improved condenser for zinc vapor. This application is a continuation in part of our application Ser. No. 678,540, filed June 22, 1946.

In the customary pyrometallurgical practices of smelting zinc ores, the zinc is recovered as molten metal by condensing the zinc vapor contained in the gaseous products of the smelting operation. In continuously operated smelting equipment, such as modern externally heated retorts or electro-thermally heated retorts, the zinc vapor diluted with ordinary smelting gases, such as carbon monoxide and the like, is passed through a. condenser in which an operating temperature is maintained for effective condensation of the zinc vapor to molten zinc. This temperature may advantageously be of the order of from 500 to 550 C. Since the gas frequently enters the condenser at a temperature at least 300 C. higher than the proper operating temperature, it is customary in such cases to thermally associate with the condenser suitable heat-dissipating means for maintaining the proper temperature, and especially is this so with zinc smelting equipment of relatively large capacity. In the copending patent application of ourselves and Harry C. Haupt, Serial No. 626,508, filed November 3, 1945, there is disclosed a splash zinc condenser in which the heat-dissipating means for the condensing chamber are cooling jackets thermally associated with the outside walls of the chamber, and in a companion application Ser. No. 633,004, filed December 5, 1945, we describe the positioning of positive artificial cooling means within the condensing chamber itself.

A characteristic feature of the splash condenser described in the aforementioned applications is the provision of a substantial volume of molten zinc in the bottom of the condensing chamber, which is kept under continuous agitation and which communicates with another body of molten zinc in a discharge well exterior of the condensing chamber. While investigating the performance of this splash condenser under commcrcial operating conditions, wev have discovered that it is possible to maintain a proper operating temperature within the condensing chamber by appropriate dissipation of heat from the body of molten metal in the discharge well. Thus, by direct artificial cooling of the molten metal in the discharge well, we have found that sumcient heat can be withdrawn from the communicating body of molten zinc in the condensing chamber to maintain the proper operating temperature of the chamber.

Accordingly, the zinc condenser of the present invention comprises a condensing chamber having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc and having a well communicating directly with said chamber adapted to hold a body of molten zinc in communication with molten zinc in the chamber. A rotor is provided with peripherally disposed pockets capable upon rotation of the rotor of agitating molten zinc in the condensing chamber to facilitate circulation of molten zinc between said bodies thereof and capable of hurling molten zinc from said body thereof within the condensing chamber into the upper portion of the chamber in the path of zinc vapor passing therethrough- Means are provided for rotating the rotor, and a cooling shell is positioned in the molten zinc in the well. Means are advantageously provided for varying the submerged area of the cooling shell in response to temperature changes in one of the bodies of molten zinc. As more fully described hereinafter, two cooling shells may be provided, one of which is relatively fixed and the other movable to vary its submerged area.

The foregoing and other novel features of the invention will be best understood from the following description taken in conjunction with the accompanying drawings, in which Fig. 1 is a longitudinal sectional elevation of a condenser embodying the invention,

Fig. 2 is a top plan view of the condenser,

Fig. 3 is a transverse sectional elevation on the section line 3-3 of Fig. 1, and

Figs. 4 and 5 are fragmentary longitudinal sectional elevation (section line 4-4 of Fig. 5) and top plan partly in section 55 of Fig. 4), respectively, of the condenser with a second cooling well at its other end.

The condenser illustrated in the drawing is of the splash type described in the aforementioned applications, to which reference is made for a fuller description of such features of construction as are not directly concerned with the present invention and hence not herein illustrated and described. As shown in the drawings, the condenser comprises a generally rectangular condensing chamber 5 having a zinc vapor inlet 6 aproximate one end and an exhaust or waste gas outlet 1 approximate its other end, and is lined with suitable refractory material. The zinc vapor inlet 6 is connected by a pipe 8 to a source of zinc vapor, such as a vertical zinc smelting retor 3 The zinc vapor inlet and the gas outlet I are shielded by depending refractory baflles 9 and Ill, respectively, to prevent splashing or spraying of molten zinc into the inlet or outlet.

The condensing chamber communicates, be-

neath the lower edge of its end wall I I. with a discharge well I2 having an overflow spout I3 determining the level (a) of'the body of molten zinc in i A collecting trough I4 the collecting chamber. receives the molten metal overflowing the spout I3 and conveys it to casting equipment or the like. The lower portion of the endwall I I dips into the molten metal between the condensing chamber and the, communicating discharge well and seals the condensing chamber from the atmosphere at this point. The overflow spout I3 and trough Il may be dispensed with, and molten metal manually dipped or otherwise suitably removed from the well I2 for casting, storage or other purpose. As zinc vapor condenses in the chamber 5, the resuiting molten zinc collects in the body of molten zinc in the chamber, and molten zinc is removed from the well I2 by continuous overflow, by dipping at periodic intervals, or in any other suitable manner to maintain, for all practical purposes, a substantially constant volume of molten zinc in the chamber.

A generally cylindrical rotor I5 is mounted within the condensing chamber 5. The rotor is carried by a hollow or axially bored metal shaft I6 mounted in bearings outside the condenser.

The shaft I6 is horizontally disposed and extends through the side walls of the condensing chamber between the zinc inlet and the gas outlet in a direction generally transverse to the direction of gas flow through the chamber. The rotor may be constructed of graphite, silicon carbide or other suitable refractory, and is separated from direct contact with.the shaft I6 by a sleeve I8 of insulating cement. The shaft I6 has a plurality of circumferentially spaced peripheral ribs I9 embedded in the cement sleeve, and the bore'of the rotor has a plurality of spaced recesses filled with the cement of the sleeve, so that the shaft, sleeve and rotor are effectively keyed together. The shaft I6 is cooled by the flow of a cooling medium, such as waten'through its axial bore.

The peripheral surface of the rotor-J5 has a plurality of circumferentially spaced pockets or cups 2 l. The pockets have a generally scoop-like section with a relatively long advancing flat sec tion and a shallow semi-circular depression at the inner end or bottom of the pocket. The shaft I6 is positioned at a level substantially above that of v the molten zinc adapted to behold in the chamber 5, and the rotor I5 is of such outside diameter that its lowermost pocket is beneath the molten zinc level (a). The shaft I6 (and hence the rotor I5) is driven by an electric motor or other suit able source of power (not shown).

Artificial cooling means are operatively associated with the discharge well [2 to cool the body of molten zinc therein. While the artificial cool-. ing means may be of any suitable type, satisfactory results are secured with a bayonet watercooler depending from a suitable support or rest ing on the refractory floor or bottom of the well. As illustrated in the drawing, a metallic (e. g. iron) cooling shell 22 of substantial width and having water inlet and outlet pipes 23 and 24, re-

spectively, is operatively supported by a frame 25 and depends into and substantially to the bottom of the well I2. Any other suitable cooling liquid may be circulated through the shell 22 instead of water.

cooling shell 22.

In the practice of the invention in the condenser illustrated in the drawing, a continuous stream of gas containing zinc vapor enters the condensing chamber beneath the baiile 9 of the inlet 6) and flows in a generally horizontal direction through the chamber and beneath the baflle I0 to the exhaust gas outlet I. Where the entering gas is derived from a vertical retort smeltin operation, it will have a temperature of around 820-900 C., and will generally contain around to zinc vapor diluted for the most part with carbon monoxide gas. The rotor I5 is rotated at a relatively high speed, say around 150-200 R. P. M., clockwise as viewed in Fig, 1, so that the pockets 2I in rapid succession pick up and throw sheets or showers of molterrzinc into the gas stream. The upwardly-directed and rapidly succeeding sheets or showers of molten metal splash into the shower or rain ofmolten metal which form ideal nuclei for the condensation and subsequent coalescence of the'zinc vapor.

The rotor I 5 agitates the body of molten zinc in the bottom of the condensing chamber and the molten metal is hence in constant motion. The temperature of this body of molten zinc may be,

for all practical purposes, taken as the operating temperature of the condensing chamber and hence of the condenser itself. In accordance with the invention, this body of molten zinc is maintained at the contemplated operating temperature by the dissipation or withdrawal of heat therefrom into the artificially cooled body of molten zinc in the discharge well. Thus, circulation of the cooling medium in the cooling shell 22 abstracts heat fromthe molten zinc in the well and as a consequence heat is withdrawn from the communicating molten zinc in the condensing chamber. Due to its agitated condition and its inherent good heat conductivity, the molten zinc in the condensing chamber readily gives up its heat to the artificially cooled communicating molten zinc in the discharge well. By properly controlling the artificial cooling applied to the molten zinc in the well, heat is withdrawn or dis-' sipated from the molten zinc in the condensing chamber in such amounts and at such a rate as to maintain the proper operating temperature of the condenser, e. g, 500 to 550 C. At this operating temperature, substantially all of the zinc vapor is condensed, the condensed molten zinc is collected in the body of molten zinc in the con-v densing chamber, and molten zinc is withdrawn from the chamber into the discharge well.

The artificial cooling to which the molten zinc in the well I2 is subjected is advantageously rege ulated by varying the submerged area of the This may be done manually by lifting or lowering the shell, or by varying its inclination. Since the operating temperature of the condenser is indicated by the temperature of the molten zinc in the condensing chamber, the artificial cooling may advantageously be regulated by that temperature as obtained from a suitably positioned pyrometer or other temperature measuring instrument. Due to the agitation of the molten zinc in thecondensing chamber, the molten zinc in the communicating well is in constant circulation and when the slight operating temperature differential between the two bodies of molten zinc for a particular condenser has been ascertained, the artificial cooling may be regulated by the temperature of the molten zinc in the well. The artificial cooling may be automatically adjusted in response to temperature changes of the molten zinc in either the condensing chamber or well. Thus, as shown in Figs. 1 and 2, the submerged area of the cooling shell 22 is automatically regulated by a temperature-responsive actuating means 28 operatively connected to a pyrometer 21 positioned in the molten zinc in the well I2. If the temperature of the molten zinc in the well rises, the actuating means 26, responding to that temperature rise, lowers the shell 22, thereby increasing its submerged area and hence its cooling effect. If, on the other hand, the temperature of the molten zinc decreases, the actuating means 26 raises the shell 22 and thereby decreases its cooling effect. In this manner, the temperature of the molten zinc in the well is maintained within predetermined limits by regulating the cooling eifect of the shell 22, and thereby the operating temperature of the condensing chamber is controlled. As previously stated, the pyrometer 21 may be positioned in the molten zinc in the condensing chamber, although it is generally more conve-' nient and equally satisfactory to position it in the molten zinc in the well.

Molten zinc may be manually or otherwise dipped from the discharge well [2, instead of overflowing the spout l3 into the trough l4. Dlpping is generally carried out at periodic but frequent intervals, and only such an amount of molten zinc is removed from the well at each dipping as to maintain, for practical purposes, a substantially constant volume of molten zinc in the condensing chamber. A certain minimum volume of molten zinc should be maintained in the well in order to provide an adequate heat reservoir for withdrawing heat from the condensing chamber and dissipating such heat through the artificial cooling means as well as to prevent freezing during such interruptions in condenser operation as occasionally occur in practice, and the depth of molten zinc in the well should be sufiicient to permit adecuate immersion of the cooling means. In practice, heat is dissipated from the molten zinc in the well at about the same rate that heat is withdrawn from the condensing chamber, and the molten zinc in the well is hence not unduly cooled. While the relative volumes of molten zinc in the condensing chamber and discharge well will depend upon the size and capacity of the condenser, and perhaps to a lesser degree upon the efiectiveness of the agitation of the molten zinc in the chamber, the following example is indicative of these factors:

The condenser was of the splash type illustrated in the drawing and had a condensing capacity of about 6 tons of zinc per day of 24 hours. About 2000-2500 pounds of molten zinc was maintained in the condensing chamber and about 500 pounds in the discharge well, and the area of communication between the two bodies of molten zinc was of the order of one-half square foot. The rotor l lifted about 5000 pounds of molten zinc per minute. In other words, molten zinc in amount approximately equivalent to the body thereof in the condensing chamber was lifted from that body and thrown into the chamber by the rotor every 30 seconds. This resulted in a vigorous agitation of the molten zinc in the chamber which was transmitted to the communicating body of molten zinc in the well. The

operating temperature of the condensing chamber was maintained slightly above 500 C. by immersion of a water-cooled shell (22) in the molten metal in the well l2, the immersion area of the shell (of theorder of about one-half square foot) being manually regu ated in accordance with the temperature of the molten zinc in the well. With continuous overflow of molten zinc from the discharge well l2 into the trough I4, the temperature of the molten zinc in the well is 10-15 C. lower than that of the molten zinc in the condensing chamber. With manual dipping from the discharge well about 400 pounds of molten zinc is removed from the well, and the depth of molten zinc in the condensing chamber drops from about '7 inches to about 6 inches.

The external and communicating body of molten zinc need not be held in the discharge well of the condenser, but may be an equivalent externally positioned auxiliary cooling well in similar communication with the condensing chamber, as for example at the opposite end or at the side of the condenser. Aside from the fact that molten zinc is not ordinarily removed from such an auxiliary cooling well, the molten zinc therein is artificially cooled and functions in the same manner as herein described with respect to the molten zinc in the discharge well l2. An adequate depth of molten zinc should be maintained in the well l2 or equivalent cooling well to permit such immers on of the artificial cooling means as is required for the practice of the invention. With a water-cooled iron shell (i2), a thin coating or crust of solidified zinc forms on the submerged area of the shell, but this does not adversely afiect the cooling efliciency, and moreover protects the iron shell from corrosion by the molten zinc. practice to use a cooling shell for the dissipation of heat from the molten zinc in the cooling well, any other appropriate cooling means may be employed. Wherever situated, the area of communication between the condensing chamber and cooling well should be substantial, and preferably as large as practical, while effectively sealing the condensing chamber against the entrance of atmospheric air, in order to provide an adequate area of heat exchange between the communicating bodies of molten zinc and to provide some agitation or circulation of the molten metal in the cooling well in consequence of the agitation of the communicating body of molten zinc in the condensing chamber.

In Figs. 4 and 5 of the drawings, the other or rearward end of the condenser is provided with a molten zinc cooling well 28 communicating with the molten zinc in the condensing chamber 5. The pipe 8, connected to the source of zinc vapor,

enters the zinc vapor inlet 6 atone side thereof.

The lower portion of the rearward end wall 29 of the condensing chamber dips into the molten zinc between the chamber and the communicating well 28 and seals the condensing chamber from the atmosphere at this point. Two artificial cooling elements 30 and 3| are associated with the molten zinc in the well 28. These elements are flat metal shells with water inlet and outlet pipes 32 and 33, respectively, and have internal bafiles 34 to provide a tortuous path for the cooling me dium. They are immersed about A to inch in the molten zinc and together cover a substantial part of the surface area of the molten metal. One element 30 is fixed in position, and the other element 3| is movable into and out of the molten zinc in response to a predetermined. decline or While it is now our preferred rise, respectively, of the temperature of the molten zinc in the well 28. Thus, the element 8|, suitably suspended, is operatively connected by a rack and pinion 88 to a temperature-responsive actuating means 88 operatively connected to a pyrometer 81 positioned in the molten zinc in the well 28. Changes in temperature of the molten zinc in the well 28 are transmitted from the pyrometer 81 to a high" and low" temperature control device 88. When the control device 88 moves to its high position it sets the actuating means 88 in operation to raise the cooling element 8| out of the molten zinc, and when the device 88 moves to its low" position, it again sets the actuating means 86 in operation to lower the cooling element 8| until it is immersed to a predetermined depth in the molten zinc. In this manner the temperature of the molten zinc in the well 28 is automatically held within a predetermined range.

Where the condenser is provided with the cooling well 28, all of the artificial cdoling and the automatic or manual control thereof may be -effected in this well. Artificial cooling may also be effected, if desired, in the discharge well l2,

and the cooling means in the well l2 may be fixed or movable, and if movable may be manually or automatically controlled.

As disclosed in the aforementioned application Ser. Nos. 626,508 and 633,004, the rotor i5 has a laterally extending sleeve 89 at each end thereof surrounding the cement sleeve I8 where the latter extends through the wall of the condenser. The rotating sleeves 39 extend through stationary sleeves 40. The outer ends ofv the concentric sleeves I8, 89 and 40 are enclosed by a seal comprising a cap 4| of moulded asbestos and a gland bushing 42 through which the shaft It extends.

The cap 4| presses tightly against the side wall of the condenser, and the space between the cap and the ends of the sleeves is filled with a suitable packing material 48 such as flake graphite. This type of seal for preventing the leakage of zinc vapor through the apertures in the side walls through which the shaft I'I extends has been found as efi'ective as and in some case preferable to the gas seal described in the aforementioned applications.

"The shaft l6, mounted in bearings 44 outside the condenser, has a drive pulley 45 secured thereto. Water inlet and outlet pipes 46 and 41, respectively, provide a flow of cooling medium through the axial bore 48 of the shaft l8.

We claim:

1. A condenser for zinc vapor comprising. a condensing chamber having a zinc inlet and a gas outlet and adapted to hold a body of molten zinc, a well communicating directly with said chamber and adapted to hold a body of molten zinc in communication with molten zinc in the chamber, a rotor provided with peripherally disposed pockets capable upon rotation of the 'rotor of agitating molten zinc in the condensing chamber to facilitate'circulation of molten zinc between said bodies thereof and capable of hurling molten zinc from said body thereof within the condensing chamber into the upper portion of the chamber in the path of zinc vapor passing therethrough,

' means for rotating said rotor, and a cooling shell positioned in the molten zinc in said well.

2. A condenser for zinc vapor comprising a con-' j densing chamber-having a zinc vapor inlet and zinc in communication with molten zinc in the chamber, a rotor provided with peripherally disposed pockets capable upon rotation of the rotor of agitating molten zinc in the condensing chamber to facilitate circulation of molten zinc between said bodies thereof and capable of hurling molten zinc from said body thereof within the condensing chamber into the upper portion of the chamber in the path of zinc vapor passing therethrough, means for rotating said rotor, a cooling shell positioned in the molten zinc in said well, and means for varying the submerged area of the cooling shell in response to temperature changes of one of said bodies of molten zinc.

3. A condenser for zinc vapor comprising a condensing chamber having a zinc vapor inlet and a gas outlet and adapted to hold a body of molten zinc, a well communicating directly with said chamber and adapted to hold a body of molten zinc in communication with molten zinc in the chamber, a rotor provided with peripherally disposed pockets capable upon rotation of the rotor of agitating molten zinc in the condensing chamber to facilitate circulation of molten zinc between said bodies thereof and capable of hurling molten zinc from said body thereof within the condensing chamber into the upper portion of the chamber in the path of zinc vapor passing therethrough, means for rotating said rotor, two cooling shells operatively associated with said well and adapted to be immersed in molten zinc therein, one of said shells being relatively fixed and the other movabie to vary the area thereof immersed in the molten zinc, and means for circulating water through said shells.

ERWIN C. HANDWERK. GEORGE T. MAHLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Tutein Nov. 11, 1947 Certiucate of Correction Patent N 0. 2,457,549. December 28, 1948.

ERWIN o. HANDWERK ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 39, before 55 insert an opening parenthesis; column 7, line 56, claim 1, after the word zinc insert vapor;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F.- MURPHY,

Assz'stan-t Oommz'ssioner of Patents. 

